linux-kernel - Re: [RFC PATCH v5 035/104] KVM: x86/mmu: Disallow dirty logging for x86 TDX

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Date:   Tue, 5 Apr 2022 15:09:31 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Jim Mattson <jmattson@...gle.com>,
        erdemaktas@...gle.com, Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 035/104] KVM: x86/mmu: Disallow dirty logging for
 x86 TDX

On 3/4/22 20:48, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> TDX doesn't support dirty logging.  Report dirty logging isn't supported so
> that device model, for example qemu, can properly handle it.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/kvm/x86.c       |  5 +++++
>   include/linux/kvm_host.h |  1 +
>   virt/kvm/kvm_main.c      | 15 ++++++++++++---
>   3 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c52a052e208c..da411bcd8cbc 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12876,6 +12876,11 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
>   }
>   EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
>   
> +bool kvm_arch_dirty_log_supported(struct kvm *kvm)
> +{
> +	return kvm->arch.vm_type != KVM_X86_TDX_VM;
> +}
> +
>   EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry);
>   EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
>   EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index a56044a31bc6..86f984e0c93f 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1423,6 +1423,7 @@ bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu);
>   int kvm_arch_post_init_vm(struct kvm *kvm);
>   void kvm_arch_pre_destroy_vm(struct kvm *kvm);
>   int kvm_arch_create_vm_debugfs(struct kvm *kvm);
> +bool kvm_arch_dirty_log_supported(struct kvm *kvm);
>   
>   #ifndef __KVM_HAVE_ARCH_VM_ALLOC
>   /*
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 3adee9c6b370..ae3bf553f215 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1423,9 +1423,18 @@ static void kvm_replace_memslot(struct kvm *kvm,
>   	}
>   }
>   
> -static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem)
> +bool __weak kvm_arch_dirty_log_supported(struct kvm *kvm)
>   {
> -	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;
> +	return true;
> +}
> +
> +static int check_memory_region_flags(struct kvm *kvm,
> +				     const struct kvm_userspace_memory_region *mem)
> +{
> +	u32 valid_flags = 0;
> +
> +	if (kvm_arch_dirty_log_supported(kvm))
> +		valid_flags |= KVM_MEM_LOG_DIRTY_PAGES;
>   
>   #ifdef __KVM_HAVE_READONLY_MEM
>   	valid_flags |= KVM_MEM_READONLY;
> @@ -1826,7 +1835,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
>   	int as_id, id;
>   	int r;
>   
> -	r = check_memory_region_flags(mem);
> +	r = check_memory_region_flags(kvm, mem);
>   	if (r)
>   		return r;
>   

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>